Backports de 3,18 geralmente funcionam bem para cartões Realtek, no terminal
wget -N -t 5 -T 10 https://www.kernel.org/pub/linux/kernel/projects/backports/stable/v3.18.1/backports-3.18.1-1.tar.xz
tar -xf backports-3.18.1-1.tar.xz
cd ~/backports-3.18.1-1
make defconfig-rtlwifi
make
sudo make install
Reinicie quando terminar